Reading a characteristic does not generate a BLE event

[only1chi]

Hi,

I think I have properly configured my application to authorize reads on characteristic, yet I do not see an event generated. I get write events, but I don't get read events. Can anyone see what I'm doing wrong, or not doing at all? Here are some code snippets from my application. 

I create custom services as follows:

ret_code_t ble_vpe_init(ble_vpe_t * p_vpe, ble_vpe_init_t * p_vpe_init)
{
    ret_code_t          err_code;
    ble_uuid_t          ble_uuid;
    ble_uuid128_t       vpe_base_uuid = VECTOR_PUMP_BASE_UUID;

    VERIFY_PARAM_NOT_NULL(p_vpe);
    VERIFY_PARAM_NOT_NULL(p_vpe_init);

    /**@snippet [Adding proprietary Service to the SoftDevice] */
    // Add a custom base UUID.
    err_code = sd_ble_uuid_vs_add(&vpe_base_uuid, &p_vpe->uuid_type);
    VERIFY_SUCCESS(err_code);

    ble_uuid.type = p_vpe->uuid_type;
    ble_uuid.uuid = BLE_UUID_VECTOR_PUMP;

    // Add service
    err_code = sd_ble_gatts_service_add(BLE_GATTS_SRVC_TYPE_PRIMARY,
                            &ble_uuid,
                            &p_vpe->service_handle);
    VERIFY_SUCCESS(err_code);

    // Add the characteristics
    err_code = vpe_command_char_add(p_vpe);

    return err_code;
}

I add the custom characteristic to the service as follows:

static ret_code_t vpe_command_char_add(ble_vpe_t *p_vpe)
{
    ret_code_t              err_code;
    uint8_t                 init_value = 0;
    ble_uuid_t              char_uuid;
    ble_uuid128_t           base_uuid = COMMAND_BASE_UUID;
    ble_add_char_user_desc_t user_desc;
    ble_gatts_attr_md_t     attr_md;
    ble_gatts_char_md_t     char_md;
    ble_gatts_attr_t        attr_char_value;

    // Add a custom base UUID.
    err_code = sd_ble_uuid_vs_add(&base_uuid, &char_uuid.type);
    VERIFY_SUCCESS(err_code);

    memset(&char_md, 0, sizeof(char_md));
    char_md.char_props.read = 1;
    char_md.char_props.write = 1;

    ble_gatts_attr_md_t cccd_md;
    memset(&cccd_md, 0, sizeof(cccd_md));
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&cccd_md.read_perm);
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&cccd_md.write_perm);
    cccd_md.vloc                = BLE_GATTS_VLOC_STACK;    
    char_md.p_cccd_md           = &cccd_md;
    char_md.char_props.notify   = 1;


    memset(&attr_md, 0, sizeof(attr_md));
    attr_md.rd_auth = 1;
    attr_md.wr_auth = 0;
    attr_md.vlen = 0;
    attr_md.vloc = BLE_GATTS_VLOC_STACK;
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md.read_perm);
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&attr_md.write_perm);


    memset(&attr_char_value, 0, sizeof(attr_char_value));
    char_uuid.uuid = BLE_UUID_VECTOR_PUMP;
    attr_char_value.p_uuid = &char_uuid;
    attr_char_value.p_attr_md = &attr_md;
    attr_char_value.init_len = BLE_COMMAND_CHAR_LEN;
    attr_char_value.init_offs = 0;
    attr_char_value.max_len = BLE_COMMAND_CHAR_LEN;
    attr_char_value.p_value = &init_value;

    err_code = sd_ble_gatts_characteristic_add(p_vpe->service_handle,
                                               &char_md,
                                               &attr_char_value,
                                               &p_vpe->command_char_handle);
    VERIFY_SUCCESS(err_code);
    return err_code;

}

I get write events, but I don't get any read events. My event handler is as follows:

void ble_vpe_on_ble_evt(ble_evt_t const * p_ble_evt, void * p_context)
{
    if ((p_context == NULL) || (p_ble_evt == NULL))
    {
        return;
    }

    ble_vpe_t * p_vpe = (ble_vpe_t *)p_context;

    switch (p_ble_evt->header.evt_id)
    {
        case BLE_GAP_EVT_CONNECTED:
          on_connect(p_vpe, p_ble_evt);
          break;

        case BLE_GATTS_EVT_WRITE:
            on_write(p_vpe, p_ble_evt);
            break;

        case BLE_GATTS_EVT_RW_AUTHORIZE_REQUEST:
            if((p_ble_evt->evt.gatts_evt.params.authorize_request.type) == BLE_GATTS_AUTHORIZE_TYPE_READ){
                NRF_LOG_INFO(0,"BLE Read request. \n");
                on_read(p_vpe, p_ble_evt);
            }
            //If there is a write request
            else if((p_ble_evt->evt.gatts_evt.params.authorize_request.type) == BLE_GATTS_AUTHORIZE_TYPE_WRITE){
                NRF_LOG_INFO(0,"BLE Write request. \n");
                on_write(p_vpe, p_ble_evt);
            }
            break;

        default:
            // No implementation needed.
            break;
    }
}

[only1chi]

Hi Hung,

I've attached my project.

Thank you.

sts-vector-pump-emulator.zip

[Hung Bui]

It seems a little bit different from the initial code you quoted in the original question. In the project in the .zip you sent you used the ble_srv library to initialize the characteristic. 
I noticed that you used :     add_char_params.p_user_descr->is_defered_read   = 1; This is the property for the user descriptor, not the characteristic value itself. You should use : 

add_char_params.is_defered_read=1;

 instead.

After changing that, i can see the read event in the log:  ble_vpe: Read Event. conn_handle: 0 

It doesn't seem you have handle the reply/confirmation for the read. You would need to implement sd_ble_gatts_rw_authorize_reply() in on_read()

[only1chi]

Hi Hung,

Thanks for your answer. I had done the exact same thing before, but I haven't seen the event.
Where in the application would I see the event? Which of the handlers?

Also in the file vpe_ble.c, there is an event handler which looks for 

BLE_GATTS_EVT_RW_AUTHORIZE_REQUEST 

I never see that event get triggered.

Could you point me to the event handler you're referring to? 

[only1chi]

I figured it out. I understand now what you're saying. 
I was using  sd_ble_gatts_value_set() function to handle the event when I should have been using sd_ble_gatts_rw_authorize_reply()

Thanks